#include<stdio.h>
int main()
{
    int i=0, m=0, n=0;
    float a=0, p=0, sum=0;
    scanf_s("%d", &n);
    for (i = 1; i <= n; i++)
    {
        m = n - i + 1;
        p = 1;
        for (m; m >= 1; m--)
        {
            p *= m;
        }
        a = 1.0 / p;
        sum += a;
    }
    printf("%.8f", sum + 1);
    return 0;
}